When Karen Maruani sends her 12-year-old son back to school this fall in a working-class district in Paris, the young Jewish mother has added new wisdom to typical back-to-school advice: He should remove his yarmulke on his way to and from the Jewish school he attends to prevent being attacked.

This is not just the admonishment of a nervous parent. Young children have congregated outside the school to taunt the Jewish pupils, she says.

And now many French Jews say the anti-Semitism that has existed for years just below the surface is boiling over after the latest deadly conflict in the Gaza Strip, which has taken nearly 2,000 lives, most of them Palestinian. The controversy is forming new divisions in France that many don’t expect to lessen even if a cease-fire between Israel and Hamas, accepted Sunday, paves the way to a truce.

Support for Israel among American Jews tends to grow with age. But in France, Jewish leaders and community members say that support for Israel is robust among both young and old – in part as a reaction to growing anti-Semitism. Unlike in the US where pacifists and Jews protest alongside Palestinians for peace, in France, even young Jews who would be the most likely to criticize Israel’s actions were they in the US have instead found themselves siding with Israel’s right to defend itself.

“We have long thought that anti-Semitic prejudices would go away with the new generation,” says Yonathan Arfi, the vice president of the Representative Council of Jewish Institutions of France. "Events [of late] show that the new generation is not at all immune to anti-Semitism, on the contrary.” He says it’s been most critical in disenfranchised neighborhoods.

Growing anti-Israel – and anti-Semitic – sentiments

Tensions from the fighting in Gaza have spread well beyond the Middle East, leading to pro-Palestinian marches that have put some European governments in uncomfortable positions. In Germany, a tinge of neo-Nazism has surfaced at some of the demonstrations against Israeli aggression. A British foreign-policy minister resigned over what she called Prime Minister David Cameron’s “morally indefensible” support of Israel.

But nowhere has the prospect for a flashpoint been greater than France, which has Europe’s largest Muslim and Jewish communities, with an estimated 2.1 million practicing Muslims and 500,000 Jews.

Tensions in France's Jewish community were already high, after a March 2012 attack on a Jewish school in Toulouse left seven dead and a May attack at a Jewish museum in Brussels killed four. That has happened against the backdrop of the political rise of the anti-immigrant National Front, which has anti-Semitic roots.

And marches this summer against Israel have devolved into anti-Semitic violence, especially after the government attempted to preemptively ban pro-Palestinian marches in July. Protesters responded with clashes in the heavily Jewish Parisian suburb of Sarcelles, known to some as “Little Jerusalem,” which also has a strong immigrant population. Some Jewish locales were specifically vandalized.

The government widely condemned those attacks, with French Interior Minister Bernard Cazeneuve responding that “nothing can justify anti-Semitism.”

But his words, and the bans on certain marches, come as a public and private wariness of Israel’s role in the conflict in Gaza grows. French President François Hollande spoke his toughest words yet against Israel’s actions, while public opinion in support of Palestinians has grown to new highs in Europe.

Although 4 in 10 Americans sympathize with Israel – far higher than anywhere else in Europe – among those who choose a side in Europe, more sympathize with Palestinians. A poll by YouGov in July, for example, showed that during the recent conflict the number of those in Britain siding with Palestinians rose to a high of 27 percent, while for Israelis it fell to a low of 12 percent. In France, support for Palestinians is 18 percent, compared with 11 percent for Israel.

'In the same basket'

At Patistory, a kosher bakery in the 19th arrondissement, owners Patrick and Martine Belaiche say that they attended a pro-Israeli assembly held in Paris in July – to counter pro-Palestinian marches – to “show that we are here,” says Mr. Belaiche.

He says Jews and Muslims in France have a lot more similarities than differences. “We’re in the same basket, Jews and Muslims. Normally those who don’t like Jews also don’t like Arabs because we are not like ‘them.’”

But the “us” versus “them” has become a powerful theme that has touched the lives of youths, including their five adult children. Mrs. Belaiche worries incessantly that her daughters will be attacked, and both parents advise their son to cover his yarmulke with a cap while on the metro or not wear it at all, as Ms. Maruani advised her son. “That’s not normal,” Mr. Belaiche says.

At its zenith, fear has led hundreds of French Jews to leave for Israel. The Belaiches hope to retire to Israel, too. Mr. Arfi says that Jews have always left for Israel, for spiritual and ideological reasons, but today there are also negative motivators.

“Those who are leaving are doing so for various reasons – religious, Zionist commitment, economic reasons – but also some have the feeling that the atmosphere has become hostile for them, especially in certain working-class neighborhoods.”